<style type='text/sass'>

    @for $j from 1 through 6 {
        .text-#{$j} {
            font-size: 10px * $j;
        }
    }

</style>

<p class="text-1">Hello</p>
<p class="text-2">Hello</p>
<p class="text-3">Hello</p>
<p class="text-4">Hello</p>
<p class="text-5">Hello</p>